Printed wiring board and connector connecting the wiring board

ABSTRACT

A printed wiring board ( 1 ) includes: a base substrate ( 3 ); a plurality of pads ( 15   a,    17   a ) for electrical connection that are disposed at one surface side of the base substrate ( 3 ) and at a connection end portion ( 13 ) to be connected with another electronic component ( 50 ); wirings ( 9, 11 ) that are connected with the pads ( 15   a,    17   a ); and engageable parts ( 28, 29 ) that are formed at side edge parts of the connection end portion ( 13 ) and are to be engaged with engagement parts ( 58 ) of the other electronic component ( 50 ) in the direction of disconnection. The flexible printed wiring board ( 1 ) further includes reinforcement layers ( 31, 32 ) that are disposed at the other surface side of the base substrate ( 3 ) and at a frontward side with respect to the engageable parts ( 28, 29 ) when viewed in the direction of connection with the other electronic component, and that are formed integrally with the wirings ( 9 ).

TECHNICAL FIELD

The present invention relates to a printed wiring board having pads forelectrical connection at a connection end portion to be connected withanother electronic component, such as a connector, and also relates to aconnector that connects the printed wiring board with another wiringboard.

BACKGROUND ART

Printed wiring boards are used for connection between electroniccomponents in electronic devices, such as digital cameras, digital videocamcorders, notebook-sized personal computers, cellular phones, and gamemachines. In accordance with reduction in weight, thickness and size ofsuch electronic devices, it is also required to make printed wiringboards thin and small in themselves. However, if a printed wiring boardis made thin and small, the holding force given by a connector to theconnection end portion will be weak, and troubles may possibly occur,including that the printed wiring board is disconnected from theconnector and contact failure occurs during implementation such as dueto reaction forces in wiring and impact of dropping or the like.

To prevent such disconnection of a printed wiring board, Patent Document1 below describes providing notches at locations opposite to each otherat a pair of parallel sides of a flexible printed wiring board, andfitting engagement parts provided on a connector into the notchesthereby to hold the flexible printed wiring board in the housing of theconnector.

PRIOR ART DOCUMENT Patent Document

[Patent Document 1] JP 2009-80972 A

SUMMARY OF INVENTION Problems to be Solved by Invention

In the disclosure of the above Patent Document 1, however, the sidesformed with the notches are constituted only of a base film andcoverlays which cover both surfaces of the base film, and the base filmand coverlays are each formed of a thin film of polyimide. Therefore,when the thickness of the film is made thin in accordance with furtherreduction in thickness and size of the printed wiring board, asufficient strength cannot be provided around the notches, and it willbe difficult to ensure a sufficient holding force given by the connectorto the printed wiring board.

Accordingly, problems to be solved by the present invention includeproviding a printed wiring board which exhibits excellent disconnectionresistance.

Means for Solving Problems

The present invention provides a printed wiring board comprising: a basesubstrate; a plurality of pads for electrical connection that aredisposed at one surface side of the base substrate and at a connectionend portion to be connected with another electronic component; wiringsthat are connected with the pads; and an engageable part that is formedat the connection end portion and is to be engaged with an engagementpart of the other electronic component in a direction of disconnection.The printed wiring board of the present invention is characterized byfurther comprising a reinforcement layer that is disposed at the othersurface side of the base substrate and at a frontward side with respectto the engageable part when viewed in a direction of connection with theother electronic component and that is formed integrally with any of thewirings.

In the present description herein, the term “frontward” or “front”refers to the direction toward the front-end side of the connection endportion of the printed wiring board, while the term “rearward” or “rear”refers to the opposite direction.

In the printed wiring board of the present invention, it is preferredthat the reinforcement layer has the same thickness as that of thewirings.

In the printed wiring board of the present invention, it is preferredthat the engageable part and the reinforcement layer are provided ateach of both side edge parts of the connection end portion.

In the printed wiring board of the present invention, it is preferred toprovide another reinforcement layer that is disposed at the one surfaceside of the base substrate and at a frontward side with respect to theengageable part when viewed in the direction of connection with theother electronic component and that is separated from the reinforcementlayer provided at the other surface side.

In the printed wiring board of the present invention, it is preferredthat the reinforcement layer at the one surface side is formedintegrally at least with any of the pads and wirings.

In an alternative embodiment of the printed wiring board of the presentinvention, it is preferred that the reinforcement layer at the onesurface side is formed separately from the pads and wirings.

In the printed wiring board of the present invention, it is preferred toprovide an insulating layer that covers a surface of the reinforcementlayer provided at the one surface side.

In the printed wiring board of the present invention, it is preferredthat the engageable part is a notched part formed at a side edge part ofthe connection end portion.

In the printed wiring board of the present invention, it is preferredthat the printed wiring board is a flexible printed wiring board.

The present invention also relates to a connecter which connects theabove-described printed wiring board with another wiring board. Theconnector is characterized by comprising: a housing that has aninsertion opening into which the connection end portion of the printedwiring board is inserted; a plurality of contacts that are provided tocorrespond to the plurality of pads of the printed wiring board insertedin the housing; and the engagement part that engages with the engageablepart provided with the printed wiring board in the direction ofdisconnection of the printed wiring board.

In the connector of the present invention, it is preferred to provide anoperative member for connection and disconnection of the contacts andthe printed wiring board.

In the connector of the present invention, it is preferred that theoperative member is a rotative member that is rotatably supported by thehousing around a rotation axis in a width direction and is operative to:rotate in one direction thereby to connect the contacts with the pads ofthe printed wiring board; and rotate in the other direction thereby todisconnect the contacts from the pads of the printed wiring board.

In the connector of the present invention, it is preferred that theengagement part is a lock member that is configured such that, as therotative member rotates in the one direction, the lock member engageswith the engageable part, which is provided at least at one side edgepart of the connection end portion of the printed wiring board, in thedirection of disconnection of the printed wiring board, and as therotative member rotates in the other direction, the engagement isreleased.

Effect of Invention

The printed wiring board of the present invention has a feature that theengageable part is provided at the connection end portion so as to beengaged with the engagement part of the other electronic component inthe direction of disconnection as well as a feature that thereinforcement layer is provided at the other surface side of the basesubstrate and at the frontward side with respect to the engageable part.According to the features of the present invention, the strength of theprinted wiring board frontward with respect to the engageable part canbe enhanced, and a sufficient engagement force (disconnectionresistance) with the engagement part of the other electronic componentcan be ensured even when the printed wiring board is made thin andsmall.

Moreover, according to the present invention, the reinforcement layer isformed integrally with any of the wirings for pads thereby to allow thesurface area of the reinforcement layer to be large. In addition, sincethe reinforcement layer is supported by the wiring or wirings, a higherdisconnection resistance can be achieved compared with a case in whichthe reinforcement layer is formed separately from the wirings for pads.Furthermore, in the situation that the engagement part of the otherelectronic component such as a connector is ordinarily connected toground, the reinforcement layer is disposed at the opposite side of thebase substrate to the side provided with the pads and is not to be indirect contact with the engagement part of the other electroniccomponent, and the wirings for signals can therefore be prevented fromshort-circuiting with the ground via the reinforcement layer and theengagement part of the other electronic component.

BRIEF DESCRIPTION OF DRAWING(S)

FIG. 1 is a plan view showing a part of a flexible printed wiring boardaccording to an embodiment of the present invention.

FIG. 2 is a bottom view of the flexible printed wiring board shown inFIG. 1.

FIG. 3 is a cross-sectional view along line A-A in FIG. 1.

FIG. 4 is a perspective view schematically showing pads of a front arrayand pads of a rear array that are provided on a connection end portionof the flexible printed wiring board of FIG. 1, wirings that are locatedat the back surface side and connected with the pads, and areinforcement layer that is provided at the back surface side of a basefilm.

FIG. 5 shows a modified embodiment of the flexible printed wiring boardof FIG. 1, wherein FIG. 5(a) is a plan view and FIG. 5(b) is a bottomview.

FIG. 6 is a partial bottom view showing a modified embodiment of anengageable part provided at a connection end portion of a flexibleprinted wiring board according to the present invention.

FIGS. 7(a) to 7(c) are partial bottom views showing modified embodimentsof a reinforcement layer at the back surface side of a flexible printedwiring board according to the present invention.

FIG. 8 is a set of views showing a modified embodiment of the flexibleprinted wiring board of FIG. 1, wherein FIG. 8(a) is a plan view andFIG. 8(b) is a cross-sectional view along line B-B in FIG. 8(a).

FIG. 9 is a set of cross-sectional views showing a part of productionprocess for the flexible printed wiring board shown in FIG. 1.

FIGS. 10(a) and 10(b) are cross-sectional views, at the same position asthat in FIG. 3, showing modified embodiments of the flexible printedwiring board of FIG. 1.

FIGS. 11(a) and 11(b) are cross-sectional views, at the same position asthat in FIG. 3, showing modified embodiments of the flexible printedwiring board of FIG. 1.

FIG. 12 is a set of views showing a flexible printed wiring boardaccording to another embodiment of the present invention, wherein FIG.12(a) is a plan view and FIG. 12(b) is a bottom view.

FIG. 13 is a set of views showing a flexible printed wiring boardaccording to another embodiment of the present invention, wherein FIG.13(a) is a plan view and FIG. 13(b) is a bottom view.

FIG. 14 is a set of views showing a flexible printed wiring boardaccording to another embodiment of the present invention, wherein FIG.14(a) is a plan view and FIG. 14(b) is a bottom view.

FIG. 15 is a set of views showing a flexible printed wiring boardaccording to another embodiment of the present invention, wherein FIG.15(a) is a plan view and FIG. 15(b) is a bottom view.

FIG. 16 is a plan view showing a flexible printed wiring board accordingto another embodiment of the present invention.

FIGS. 17(a) and 17(b) are partially cross-sectional perspective viewseach showing a flexible printed wiring board according to anotherembodiment of the present invention.

FIGS. 18(a) and 18(b) are partially cross-sectional perspective viewseach showing a flexible printed wiring board according to anotherembodiment of the present invention.

FIG. 19 is a perspective view showing a flexible printed wiring boardaccording to the present invention and a connector, which is applicableto the flexible printed wiring board, according to an embodiment of thepresent invention.

FIGS. 20(a) and 20(b) are perspective views showing two types ofcontacts provided in the connector of FIG. 19.

FIG. 21 is a cross-sectional perspective view showing a state in whichthe flexible printed wiring board of FIG. 1 inserted in the connectorshown in FIG. 19 is engaged with a lock member of the connector.

FIG. 22 is a cross-sectional perspective view showing a state in which arotative member of the connector shown in FIG. 19 stands up.

FIG. 23 is a perspective view showing a connector of another embodimentof the present invention, which is applicable to the flexible printedwiring board according to the present invention.

FIG. 24 is a set of cross-sectional views of the connector shown in FIG.23, wherein FIG. 24(a) is a cross-sectional view showing a state beforethe flexible printed wiring board is inserted in a housing of theconnector, and FIG. 24(b) is a cross-sectional view showing a state inwhich the flexible printed wiring board is inserted in the housing andpressed by a slider.

FIG. 25 is a plan view showing a part of a flexible printed wiring boardof Comparative Example 1.

MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. While the description herein exemplifies aflexible printed wiring board (FPC) as a printed wiring board, thepresent invention is applicable to any other printed wiring board, suchas a rigid flexible printed wiring board. In the description below, aspecific example is described in which a flexible printed wiring boardis inserted in a ZIF (Zero Insertion Force) connecter and used, but theprinted wiring board of the present invention can also be used for anon-ZIF connector which utilizes the thickness of a printed wiring boardto obtain a fitting force, and a backboard connector.

(Flexible Printed Wiring Board)

As shown in FIGS. 1 to 4, flexible printed wiring board 1 of the presentembodiment comprises: a base film 3 as a base substrate; a firstcoverlay (referred to as an “upper surface side coverlay” fordescriptive purposes, hereinafter) 5 that is attached via an adhesivelayer 4 to one surface (upper surface herein) of the base film 3 so asto cover the one surface; and a second coverlay (referred to as a “lowersurface side coverlay” for descriptive purposes, hereinafter) 7 that isattached via an adhesive layer 6 to the other surface (lower surfaceherein) of the base film 3 so as to cover the other surface. The basefilm 3 is formed of an insulating resin having flexibility, and examplesthereof include polyimide, polyester, and polyethylene naphthalate. Eachof the upper surface side coverlay 5 and the lower surface side coverlay7 can be formed by attaching a film of insulating resin, such aspolyimide, to the base film 3, or may otherwise be formed by applying athermoset ink, ultraviolet curable ink, or photosensitive ink to thebase film 3 and curing the ink.

The flexible printed wiring board 1 has a connection end portion 13,which is to be inserted in an insertion opening of a connector as willbe described later, at least at one end portion in an insertiondirection (direction of connection) I. The upper surface side of theconnection end portion 13 is not covered by the coverlay 5, and theexposed part of the connection end portion 13 is formed thereon with aplurality of pads 15 a and 17 a for electrical connection that aredisposed in a staggered arrangement to form front and rear two arrays 15and 17 when viewed in the insertion direction I. As will be understood,the pads 15 a and 17 a may not be disposed in a staggered arrangement.In an alternative embodiment, positions of the pads 15 a of the frontarray 15 in the width direction (direction crossing the insertiondirection I) W may be the same as those of the pads 17 a of the reararray 17 (see FIG. 5). According to such disposition of pads, the widthof the flexible printed wiring board 1 can be reduced, compared with acase of disposing the same number of pads in a staggered arrangement.Plated layers (e.g., gold plated layers) 18 and 19 are formed on theuppermost surfaces of the pads 15 a of the front array 15 and the pads17 a of the rear array 17. It is sufficient if the plated layers 18 and19 of the uppermost surfaces have at least electrical conductivity, butit is preferred that the plated layers 18 and 19 further haveappropriate properties, such as corrosion resistance and wearresistance. Examples of the plated layers 18 and 19 include conductivecarbon layers and solder layers in addition to the gold plated layers.The lowermost layer of the connection end portion 13 is provided with areinforcement film 23 which is attached to the lower surface of thelower surface side coverlay 7 via an adhesive layer 21. Thereinforcement film 23 can be formed of polyimide, for example.

The flexible printed wiring board 1 further has first wirings 9connected with the pads 15 a of the front array 15 and second wirings 11connected with the pads 17 a of the rear array 17. In the embodimentshown in FIG. 1, both the first wirings 9 and the second wirings 11 aredisposed at the opposite side of the base film 3 to the side providedwith the pads 15 a and 17 a, i.e., disposed between the base film 3 andthe lower surface side coverlay 7. When both the first wirings 9 and thesecond wirings 11 are disposed at the back surface side of the base film3 as in the present embodiment, the upper surface side coverlay 5 maynot be provided. The first wirings 9 and the second wirings 11 areadjacent to one another in the width direction (direction crossing theinsertion direction I) W and extend in the insertion direction(direction of connection) I to the connector. The first wirings 9 andthe second wirings 11 can be formed of known conductive metal, e.g.,copper or copper alloy. In addition, plated layers (e.g., copper platedlayers) 43 may be formed on outer surfaces of the first wirings 9 andsecond wirings 11.

As shown in FIG. 3 and FIG. 4, each pad 15 a of the front array 15 andeach first wiring 9 disposed at the lower surface side (other surfaceside) of the base film 3 are connected with each other via a via 24 thatpenetrates the base film 3. Likewise, each pad 17 a of the rear array 17and each second wiring 11 disposed at the lower surface side of the basefilm 3 are connected with each other via a via 25 that penetrates thebase film 3. In the embodiment shown, one via 24 and one via 25 areprovided for each pad 15 a and each pad 17 a, respectively, but two ormore vias 24 and two or more vias 25 may be provided for each pad 15 aand each pad 17 a, respectively, in view of improving the stability ofthe pads 15 a and 17 a, reducing the electrical resistance, etc.

As shown in FIG. 4, in the present embodiment, each first wiring 9 andeach second wiring 11 have expanded-width parts 9 a and 11 a,respectively, at positions corresponding to each pad 15 a and each pad17 a of the upper side. The expanded-width parts 9 a and 11 a havefunctions as reinforcement materials to maintain the thickness of theflexible printed wiring board 1 constant at locations of the pads 15 aand 17 a, i.e., to improve creep resistance, and are not in directcontact with the contacts of another electronic component. Ifexpanded-width parts or reinforcement materials are not present atpositions at the back surface side of the base film 3 corresponding tothe pads 15 a and 17 a at the top surface side, creep deformation of theadhesive layer included in the flexible printed wiring board 1 willoccur particularly under a high temperature environment to make thethickness of the flexible printed wiring board 1 ununiform, possiblyresulting in poor electrical contact properties. In the presentembodiment, the expanded-width parts 9 a and 11 a have a shape thatcorresponds to the shape of the pads 15 a and 17 a located above, i.e.,a shape that is substantially the same as the shape of the pads 15 a and17 a. In an alternative embodiment, however, the expanded-width parts 9a and 11 a may be formed smaller or larger than the pads 15 a and 17 alocated above, provided that the stability of contact between the pads15 a and 17 a and the contacts of another electronic component does notdeteriorate. In the present invention, the expanded-width parts 9 a and11 a may not be provided.

As shown in FIG. 1 and FIG. 2, the flexible printed wiring board 1 ofthe present embodiment has, at least at one of side edge parts (endedges in the width direction) of the connection end portion 13,specifically at both side edge parts herein, engageable parts 28 and 29that are to be engaged with engagement parts of another electroniccomponent as an object of connection (e.g., tab-like lock membersprovided with a connector to be described later) in the direction ofdisconnection (which is the opposite direction to the direction ofconnection). In the embodiment shown in FIG. 1 and FIG. 2, theengageable parts 28 and 29 are provided as notched parts formed at theside edge parts of the connection end portion 13, but the presentinvention is not limited thereto. In an alternative embodiment, theengageable parts 28 and 29 may be provided as through-holes 28 as shownin FIG. 6 or blind holes (not shown).

As shown in FIG. 2 and FIG. 4, the flexible printed wiring board 1 ofthe present embodiment has reinforcement layers 31 and 32 that areformed integrally with wirings, specifically with the first wirings 9herein, at least at the frontward side with respect to the engageableparts 28 and 29 when viewed in the direction of connection with anotherelectronic component and between the base film 3 and the lower surfaceside coverlay 7.

The reinforcement layers 31 and 32 may have the same thickness as thatof the wirings 9 and 11, but can also be formed thicker or thinner thanthe wirings 9 and 11, provided that a necessary strength is obtained. Inview of ensuring a sufficient disconnection strength, the width (lengthalong the width direction W) of the reinforcement layers 31 and 32 maypreferably be 100% or more of the width of the engageable parts 28 and29. The length (length along the insertion direction I) of thereinforcement layers 31 and 32 can be appropriately set in accordancewith various conditions (such as strength and material). The shape ofthe reinforcement layers 31 and 32 is rectangular in the embodimentshown, but the present invention is not limited thereto. In alternativeembodiments, various shapes can be employed, such as a shape having anarc as a part thereof as shown in FIG. 7(a) and shapes surrounding theengageable parts 28 and 29 as shown in FIGS. 7(b) and 7(c). Thereinforcement layers 31 and 32 may be disposed so as not to be exposedat the end edges of the engageable parts 28 and 29, such as shown inFIG. 6 and FIG. 7(a). In such cases, when the flexible printed wiringboard 1 is punched out into a final shape using a metal die at the timeof production, the metal die does not directly shear the copper foil, sothat the life of the metal die will be extended and the productionfailure such as burrs can be prevented.

The flexible printed wiring board 1 of the present embodiment with theabove structure has a feature that the engageable parts 28 and 29 areprovided at the side edge parts of the connection end portion 13 so asto be engaged with the engagement parts of another electronic componentin the direction of disconnection as well as a feature that thereinforcement layers 31 and 32 are provided at the other surface side ofthe base film 3 and at the frontward side with respect to the engageableparts 28 and 29. According to the features of the present embodiment,the strength of the frontward side of the flexible printed wiring board1 with respect to the engageable parts 28 and 29 can be enhanced, and asufficient engagement force (disconnection resistance) with theengagement parts of the other electronic component can be ensured evenwhen the flexible printed wiring board 1 is made thin and small.Moreover, the reinforcement layers 31 and 32 are formed integrally withthe wirings 9 for pads 15 a thereby to allow the surface area of thereinforcement layers 31 and 32 to be large. In addition, since thereinforcement layers 31 and 32 are supported by the wirings 9, a higherdisconnection resistance can be achieved compared with a case in whichthe reinforcement layers 31 and 32 are formed separately from thewirings 9. Furthermore, even when the engagement parts of the otherelectronic component are connected to ground, the pads 15 a and 17 a forsignals can be prevented from short-circuiting with the ground via thereinforcement layers 31 and 32 and the engagement parts of the otherelectronic component because the reinforcement layers 31 and 32 arelocated at the back surface side of the base film 3 and are not to be indirect contact with the engagement parts.

The flexible printed wiring board 1 of the present embodiment has afeature that both of the first wirings 9 connected to the pads 15 a ofthe front array 15 and the second wirings 11 connected to the pads 17 aof the rear array 17 are disposed on the other surface (back surface) ofthe base film 3. According to the feature of the present embodiment,wirings at the top surface side of the flexible printed wiring board 1can be omitted, and an advantage is thus obtained that a wide space formounting can be ensured when other electronic components such as chipsare mounted on the top surface side.

The flexible printed wiring board 1 of the present embodiment has afeature that the expanded-width parts 9 a and 11 a are provided atpositions of the first wirings 9 and second wirings 11 correspondingrespectively to the pads 15 a and 17 a. According to the feature of thepresent embodiment, even if the contacts of another electronic componentto be in contact with the pads 15 a and 17 a are misaligned to someextent from the normal positions in the pads such as due to productionerror, the stable connection of the pads 15 a and 17 a with the contactsof the other electronic component can be maintained for a long period oftime, because the thickness of a part of the flexible printed wiringboard 1 to be in contact with the contacts can be uniform, i.e., thecreep resistance can be improved. In particular, the expanded-widthparts 9 a and 11 a may have the shapes corresponding to shapes of thepads 15 a and 17 a, as in the present embodiment, thereby to moresteadily obtain that effect.

The flexible printed wiring board 1 of the present embodiment has afeature that the reinforcement layers 31 and 32 have the same thicknessas that of the wirings 9 and 11 located on the same plane. According tothe feature of the present embodiment, the flexible printed wiring board1 can have a sufficient thickness at locations to be in contact with theengagement parts of another electronic component, and the disconnectionresistance of the flexible printed wiring board 1 can be furtherenhanced.

The flexible printed wiring board 1 of the present embodiment has afeature that the engageable parts 28, 29 and the reinforcement layers31, 32 are provided at both side edge parts of the connection endportion 13. According to the feature of the present embodiment, thedisconnection resistance of the flexible printed wiring board 1 can befurther enhanced, and more stable holding can be achieved.

The above description is directed to an embodiment in which, as shown inFIGS. 1 to 4, both the first wirings 9 and the second wirings 11 aredisposed at the back surface side of the base film 3. In contrast, asshown in FIG. 5 and FIGS. 8(a) and 8(b), the disposition of the firstwirings 9 and second wirings 11 may be modified such that the secondwirings 11 are disposed at the top surface side (one surface side) ofthe base film 3 while the first wirings 9 are disposed at the backsurface side (the other surface side) of the base film 3. In the case ofFIG. 5 herein, the first wirings 9 provided at the back surface side ofthe base film 3 are used to form expanded-width parts 9 a correspondingto pads 15 a of a front array 15 and expanded-width parts 9 bcorresponding to pads 17 a of a rear array 17. In the case of FIG. 8,although not shown in detail, expanded-width parts 9 a as shown in FIG.4 may be provided on the locations at the back surface sidecorresponding to pads 15 a of a front array 15, and reinforcementmaterials (not shown) may be provided, as substitute for theabove-described expanded-width parts 11 a, on the locations at the backsurface side corresponding to pads 17 a of a rear array 17. In analternative embodiment, the first wirings provided at the back surfaceside of the base film 3 as shown in FIG. 5 may be used to formexpanded-width parts corresponding to pads 15 a of a front array 15 andexpanded-width parts corresponding to pads 17 a of a rear array 17. Theabove reinforcement materials can be formed of the same material as thatof the wirings 9 and 11, but can also be formed of other material, suchas resin, which has creep resistance, because the reinforcementmaterials are not parts of the wirings 9 and 11.

(Method for Producing Flexible Printed Wiring Board)

An embodiment of a method for producing the flexible printed wiringboard 1 shown in FIGS. 1 to 4 will now be described with reference toFIG. 9 to FIG. 11 and FIG. 3.

First, as shown in FIG. 9(a), a double-sided copper clad laminate 39 isformed as a starting material in which both surfaces of a base film 3 ofpolyimide is laminated with copper foils 36 and 37. The double-sidedcopper clad laminate 39 may be obtained by depositing or sputteringcopper on the base film 3 and thereafter performing copper plating, ormay otherwise be obtained by attaching the copper foils 36 and 37 to thebase film 3 via an adhesive or the like. Then, as shown in FIG. 9(b),blind via holes 41 and 42 are formed to pass through the copper foil 37and the base film 3 in the double-sided copper clad laminate 39 atpredetermined positions, such as by laser machining and CNC drilling,from below (from the lower surface side).

Next, as shown in FIG. 9(c), a process of DPP (Direct Plating Process)is performed to form conductive layers on the inner circumferentialsurfaces of the blind via holes 41 and 42, followed by formation of acopper plated layer 43 on the whole surface of the double-sided copperclad laminate 39 including the inner surfaces of the blind via holes 41and 42. When forming the copper plated layer 43, a scheme of so-calledbutton plating may be employed to partially plate a specific structure.Through the above operation, vias 24 and 25 are formed to electricallyconnect the upper surface side copper foil 36 of the double-sided copperclad laminate 39 with the lower surface side copper foil 37. The vias 24and 25 may be hollow vias obtained by only plating the innercircumferential surfaces of the blind via holes 41 and 42, or may alsobe so-called filled vias obtained by filling the blind via holes 41 and42 with plated materials or conductive materials. Subsequently, as shownin FIG. 9(d), the upper surface side copper foil 36 and the lowersurface side copper foil 37 are patterned to form pads 48 and 49 on thetop surface of the base film 3 and form wiring patterns 46 and 47 at thelower surface side of the base film 3 and reinforcement layers (notshown) at the back surface side. The patterning of the upper surfaceside copper foil 36 and lower surface side copper foil 37 can beperformed by forming mask patterns on the surfaces of the upper surfaceside copper foil 36 and lower surface side copper foil 37 usingphotolithography technique, for example, and thereafter etching theupper surface side copper foil 36 and lower surface side copper foil 37.

Then, an upper surface side coverlay 5 and a lower surface side coverlay7 (see FIG. 3) are attached, via adhesives, to both surfaces of thedouble-sided copper clad laminate 39 formed with the wiring patterns.

Subsequently, gold plated layers 18 and 19 are formed on the surfaces ofthe pads 15 a and 17 a formed at the upper surface side, and both sideedge parts of the connection end portion are partially removed such asusing metal dies, thereby to form engageable parts 28 and 29 at the bothside edge parts. The flexible printed wiring board 1 as shown in FIGS. 1to 4 is thus completed. In an alternative embodiment, the blind viaholes 41 and 42 may be formed from above (from the upper surface side)as shown in FIG. 10(a), or may also be formed as through holes as shownin FIG. 10(b). As described above, the copper plated layer 43 may not beformed on the whole surface of the double-sided copper clad laminate 39.For example, the copper plated layer 43 may be formed only within theregion of the connection end portion 13 (double-sided partial plating)as shown in FIG. 11(a), or may also be formed only on the upper surfaceside copper foil 36 within the region of the connection end portion 13(single-sided partial plating) as shown in FIG. 11(b).

(Flexible Printed Wiring Boards of Other Embodiments)

Flexible printed wiring boards of other embodiments according to thepresent invention will then be described with reference to FIG. 12 toFIG. 16. Similar elements to those in the flexible printed wiring board1 of the previous embodiment are denoted by the same reference numerals,and the descriptions thereof are omitted.

The flexible printed wiring board 1 of the previous embodiment has thereinforcement layers 31 and 32 only at the back surface side (othersurface side) of the base film 3, but the flexible printed wiring board1 shown in FIGS. 12(a) and 12(b) is different from the previousembodiment in an aspect that the flexible printed wiring board 1 notonly has the reinforcement layers 31 and 32 (referred also to as “firstreinforcement layers 31 and 32,” hereinafter) at the back surface side,but also has reinforcement layers 34 and 35 (referred also to as “secondreinforcement layers,” hereinafter) at the top surface side (one surfaceside) of the base film 3.

In more detail, the second reinforcement layers 34 and 35 are providedat least at the frontward side with respect to the engageable parts 28and 29, which are formed at the side edge parts of the connection endportion 13, and at the side of the surface on which the pads 15 a and 17a are provided, and are formed integrally with pads, specifically hereinwith the outermost pads 15 a of the pads 15 a of the front array 15 inthe width direction.

According to this feature of the present embodiment, the secondreinforcement layers 34 and 35, together with the first reinforcementlayers 31 and 32, can further enhance the disconnection resistance ofthe flexible printed wiring board 1.

In the embodiment of FIGS. 12(a) and 12(b), both the first wirings 9 andthe second wirings 11 are disposed at the back surface side of the basefilm 3, but as in FIG. 5 and FIG. 8, the first wirings 9 may be disposedat the back surface side of the base film 3 while the second wirings 11may be disposed at the top surface side of the base film 3 (not shown).

Referring next to FIGS. 13(a) and 13(b) which show a modified embodimentof the flexible printed wiring board shown in FIG. 12, the flexibleprinted wiring board 1 of FIGS. 13(a) and 13(b) is different from theflexible printed wiring board 1 of FIG. 12 in an aspect that theflexible printed wiring board 1 has insulating layers 5 a and 5 b on thesurfaces of the second reinforcement layers 34 and 35, respectively.

In more detail, the insulating layers 5 a and 5 b are configured suchthat the outer side parts of the upper surface side coverlay 5 in thewidth direction are extended frontward so as not to overlap the pads 15a and 17 a and the extended parts cover the upper surfaces of the secondreinforcement layers 34 and 35.

According to this feature of the present embodiment, the secondreinforcement layers 34 and 35, together with the first reinforcementlayers 31 and 32, can further enhance the disconnection resistance ofthe flexible printed wiring board 1, and even when the engagement partsof another electronic component are connected to ground, the pads 15 afor signals can be prevented from short-circuiting with the ground viathe second reinforcement layers 34 and 35 and the engagement partsbecause the engagement parts are insulated from the second reinforcementlayers 34 and 35 by the insulating layers 5 a and 5 b. Furthermore, suchinsulating layers 5 a and 5 b also serve as reinforcement layers thatenhance the strength around the engageable parts 28 and 29, and canfurther enhance the disconnection resistance of the flexible printedwiring board 1.

In the embodiment of FIGS. 13(a) and 13(b), both the first wirings 9 andthe second wirings 11 are disposed at the back surface side of the basefilm 3, but as in FIG. 5 and FIG. 8, the first wirings 9 may be disposedat the back surface side of the base film 3 while the second wirings 11may be disposed at the top surface side of the base film 3 (not shown).In the embodiment of FIG. 13, the insulating layers 5 a and 5 b are eachformed as an additional part of the upper surface side coverlay 5, butthe present invention is not limited thereto. In an alternativeembodiment, insulating layers different from the upper surface sidecoverlay 5 may be attached to the upper surfaces of the secondreinforcement layers 34 and 35 in a separate procedure.

Next, FIGS. 14(a) and 14(b) show still another modified embodiment ofthe flexible printed wiring board. This flexible printed wiring board 1is different from the embodiment of FIG. 12 in an aspect that theflexible printed wiring board 1 has second reinforcement layers 34′ and35′ at the top surface side of the base film 3 in addition to firstreinforcement layers 31 and 32 provided at the back surface side of thebase film 3, but the second reinforcement layers 34′ and 35′ are formedseparately from the pads 15 a and 17 a. That is, the secondreinforcement layers 34′ and 35′ are separated from the pads 15 a and 17a, and are not electrically connected with the pads 15 a and 17 a.

According to this feature of the present embodiment, the secondreinforcement layers 34′ and 35′, together with the first reinforcementlayers 31 and 32, can further enhance the disconnection resistance ofthe flexible printed wiring board 1, and even when the engagement partsof another electronic component are connected to ground, the pads 15 aand 17 a for signals can be prevented from short-circuiting with theground via the second reinforcement layers 34′ and 35′ and theengagement parts because the second reinforcement layers 34′ and 35′ arenot electrically connected with the pads 15 a and 17 a.

In the embodiment of FIGS. 14 (a) and 14(b), both the first wirings 9and the second wirings 11 are disposed at the back surface side of thebase film 3, but as in FIG. 5 and FIG. 8, the first wirings 9 may bedisposed at the back surface side of the base film 3 while the secondwirings 11 may be disposed at the top surface side of the base film 3(not shown).

Referring next to FIGS. 15(a) and 15(b) which show a modified embodimentof the flexible printed wiring board described with reference to FIG.14, the flexible printed wiring board 1 shown in FIG. 15 is differentfrom the flexible printed wiring board 1 of FIG. 14 in an aspect thatthe flexible printed wiring board 1 has insulating layers 5 a and 5 b onthe surfaces of the second reinforcement layers 34′ and 35′,respectively.

In more detail, the insulating layers 5 a and 5 b are configured suchthat the outer side parts of the upper surface side coverlay 5 in thewidth direction are extended frontward so as not to overlap the pads 15a and 17 a and the extended parts cover the upper surfaces of the secondreinforcement layers 34′ and 35′.

According to this feature of the present embodiment, the secondreinforcement layers 34′ and 35′, together with the first reinforcementlayers 31 and 32, can further enhance the disconnection resistance ofthe flexible printed wiring board 1, and the short-circuiting of thepads 15 a for signals with the ground as described above can be moresteadily prevented. Furthermore, such insulating layers 5 a and 5 b alsoserve as reinforcement layers that enhance the strength around theengageable parts 28 and 29, and can further enhance the disconnectionresistance of the flexible printed wiring board 1.

In the embodiment of FIGS. 15(a) and 15(b), both the first wirings 9 andthe second wirings 11 are disposed at the back surface side of the basefilm 3, but as in FIG. 5 and FIG. 8, the first wirings 9 may be disposedat the back surface side of the base film 3 while the second wirings 11may be disposed at the top surface side of the base film 3 (not shown).In the embodiment of FIG. 15, the insulating layers 5 a and 5 b are eachformed as an additional part of the upper surface side coverlay 5, butthe present invention is not limited thereto. In an alternativeembodiment, insulating layers different from the upper surface sidecoverlay 5 may be attached to the upper surfaces of the secondreinforcement layers 34′ and 35′ in a separate procedure.

Next, FIG. 16 shows a further modified embodiment of the flexibleprinted wiring board. The flexible printed wiring board 1 shown in FIG.16 is configured such that the outer side parts of the upper surfaceside coverlay 5 in the width direction are extended frontward so as notto overlap the pads 15 a and 17 a and the extended parts constitutereinforcement layers 5 a′ and 5 b′. Such a configuration can alsoenhance the strength of the frontward side from the engageable parts 28and 29.

Several embodiments of the flexible printed wiring boards according tothe present invention have been described hereinbefore, but the presentinvention is not limited to these embodiments. Various modifications arepossible, and the above-described embodiments can be combined at leastwith one another. The present invention can also be applied to flexibleprinted wiring boards having electromagnetic wave shield properties. Forexample, in the flexible printed wiring board 1 of which both the firstwirings 9 and the second wirings 11 are disposed at the back surfaceside of the base film 3 as shown in FIGS. 1 to 4, FIG. 12, FIG. 13, FIG.14, and FIG. 15, an electromagnetic wave shield layer 40 or 40′connected to ground may be formed on the opposite surface (uppersurface) of the base film 3 to the side on which the first wirings 9 andsecond wirings 11 are disposed, as in the flexible printed wiring board1 shown in FIG. 17(a) or 17(b). The pattern of the electromagnetic waveshield layer 40, 40′ may be, but is not particularly limited to, a solidpattern as shown in FIG. 17(a) or a mesh pattern having more flexibilityas shown in FIG. 17(b). On the other hand, in the flexible printedwiring board 1 of which the first wirings 9 and the second wirings 11are disposed on different surfaces of the base film 3 as shown in FIG. 8and FIG. 16, electromagnetic wave shield layers 40 or 40′ having anarrow width may be provided so as to be located between adjacent firstwirings 9 and between adjacent second wirings 11, as shown in FIG. 18(a)or 18(b). The electromagnetic wave shield layers 40 and 40′ may beformed by patterning the copper foils 36 and 37 of the double-sidedcopper clad laminate 39 as shown in FIG. 9 together with the wirings 9and 11 and pads 15 and 17, in which case the copper plated layer 43 onthe copper foils 36 and 37 and the gold plated layers 18 and 19 furtherthereon may be or may not be provided. When gold plated layers or otherlayers are provided, the coverlay 5 on the electromagnetic wave shieldlayers 40 or 40′ can be omitted. Although not shown, the electromagneticwave shield layers may also be formed by attaching separate components,such as those obtained by weaving copper lines, conductive fibers or thelike into mesh-like shapes and copper foils having predetermined shapes,to the base film 3.

(Connector)

The description will then be directed to a connector according to anembodiment of the present invention which connects the above-describedflexible printed wiring board 1 to another wiring board.

As shown in FIG. 19, connector 50 comprises: a housing 52 into which theflexible printed wiring board 1 is inserted; a plurality of contacts 54that are to be electrically connected with the pads 15 a and 17 a of theflexible printed wiring board 1; a rotative member 56, as an operativemember, that presses, via the contacts 54, the flexible printed wiringboard 1 inserted in the housing 52; and tab-like lock members 58 (seeFIG. 21), as engagement parts, that engage with the engageable parts 28and 29 provided at both side edge parts of the connection end portion 13of the flexible printed wiring board 1.

The housing 52 is formed of electrically insulating plastic and can bemanufactured using a known injection molding method. The material may beappropriately selected in consideration of the dimensional stability,workability, cost, and the like. Examples of the material include ingeneral polybutylene terephthalate (PBT), polyamide (66PA, 46PA), liquidcrystal polymer (LCP), polycarbonate (PC), polytetrafluoroethylene(PTFE), and composite material thereof.

The housing 52 is provided with a required number of insertion channelsin which the contacts 54 are inserted, and the rearward side of thehousing 52 is provided with an insertion opening 60 into which theflexible printed wiring board 1 is inserted.

The contacts 54 can be manufactured using a known working method, suchas press work and cutting work. The contacts 54, for which springproperty, conductivity and other appropriate properties are required,can be formed of brass, beryllium copper, phosphor bronze, or the like.As shown in FIGS. 20(a) and 20(b), two types of the contacts 54 areused, including those corresponding to the pads 15 a of the front array15 of the flexible printed wiring board 1 and those corresponding to thepads 17 a of the rear array 17, which are provided in a staggeredarrangement such that the insertion positions are staggered. The twotypes of contacts 54 a and 54 b have respective H-shaped figures thatare substantially formed with rearward side openings 62 and 63 intowhich the connection end portion 13 of the flexible printed wiring board1 is inserted and frontward side openings 67 and 68 into which a cam ofthe rotative member 56 to be described later is inserted. Likewise, thelock members 58 have H-shaped figures, as shown in FIG. 21, that aresubstantially formed with rearward side openings 58 a into which theconnection end portion 13 of the flexible printed wiring board 1 isinserted and frontward side openings 58 b into which the cam 65 of therotative member 56 to be described later is inserted. The lock members58 are disposed at both sides of the set of contacts 54.

As shown in FIG. 22, the rotative member 56 is rotatably supported atits both ends by the housing 52 around a rotation axis in the widthdirection W. The rotative member 56 has a cam 65, on the rotation axis,that is inserted into the above-described frontward side openings 67 and68 of the contacts 54 and into the frontward side openings 58 b of thelock members 58. After the flexible printed wiring board 1 is insertedin the insertion opening 60 of the housing 52, the rotative member 56 isrotated toward the direction of lying to actuate the cam 65 so that thefrontward side openings 67 and 68 of the contacts 54 and the frontwardside openings 58 b of the lock members 58 are expanded against thespring forces of the contacts 54 and the lock members 58. Through thisoperation, as shown in FIG. 21, the rearward side openings 62 and 63 ofthe contacts 54 and the rearward side openings 58 a of the lock members58 are narrowed, and the electric connection between the contacts 54 andthe flexible printed wiring board 1 and the engagement of the lockmembers 58 with the engageable parts 28 and 29 are achieved. Incontrast, when the rotative member 56 is rotated toward the direction ofstanding as shown in FIG. 22, the electric connection and the engagementof the lock members 58 are released.

The operating member may be, other than the rotative member 56 asdescribed above, a slider that is inserted into the housing to press theflexible printed wiring board to the contacts after the printed wiringboard is inserted in the housing. Specifically, a connector 70 as shownin FIG. 23 and FIG. 24 may be configured to mainly comprise a housing72, contacts 74, and a slider 76. The contacts 74 have substantiallyC-shaped figures, as shown in FIG. 24, and are each mainly configured ofa contacting part 74 a that comes into contact with the flexible printedwiring board 1, a connecting part 74 b that is connected with asubstrate or the like, and a fixed part 74 c that is fixed to thehousing 72 such as by press fitting. The slider 76 has a substantiallywedge-shaped figure, as shown in FIG. 24. After the flexible printedwiring board 1 is inserted in the housing 72 provided with a requirednumber of the contacts 74, the slider 76 is inserted into the housing72. Such a slider 76 mainly comprises mounted parts 76 a that aremounted to the housing 72, and a pressing part 76 b that presses theflexible printed wiring board 1 to the contacting parts 74 a of thecontacts 74. Before the flexible printed wiring board 1 is inserted, theslider 76 is in a state of being provisionally mounted to the housing72. When the slider 76 is inserted after the flexible printed wiringboard 1 is inserted, the pressing part 76 b of the slider 76 is insertedparallel to the flexible printed wiring board 1, as shown in FIG. 24(b),and the flexible printed wiring board 1 comes to be pressed to thecontacting parts 74 a of the contacts 74. Although not shown, like theconnector 50 of the previous embodiment, the connector 70 of the presentembodiment also has engagement parts that, when the slider 76 isinserted, engage with the engageable parts 28 and 29 provided with theflexible printed wiring board 1.

In the connector 50 shown in FIGS. 19 to 22, the rotative member 56 hasbeen exemplified as being disposed at a frontward position on thehousing 52 with respect to the insertion direction, but the rotativemember 56 may also be disposed at a rearward position on the housing 52with respect to the insertion direction (not shown).

EXAMPLES

Tests for confirming the effects of the present invention wereperformed, which will be described below.

Example 1

As Example 1, a printed wiring board having the structure shown in FIGS.1 to 4 was experimentally manufactured. Specifically, the flexibleprinted wiring board was manufactured such that: the connection endportion had pads disposed in a staggered arrangement to form 15 pads ofthe front array and 14 pads of the rear array; the pitch of the pads was0.175 mm (0.35 mm in each array); both the wirings for the pads of thefront array and the wirings for the pads of the rear array were providedon the surface (back surface) of the base film opposite to the surfaceprovided with the pads; and reinforcement layers formed integrally withthe wirings were provided at the back surface side and at the frontwardside with respect to notched parts (engageable parts). The pads, wiringsand reinforcement layers were made of copper, and gold plated layerswere formed on the top surfaces of the pads. A polyimide film having athickness of 20 μm was used as the base film. A polyimide film having athickness of 12.5 μm was used as each of the upper surface side coverlayand the lower surface side coverlay. A polyimide film having a thicknessof 12.5 μm was used as the reinforcement film. The reinforcement layerswere made to have a width of 0.5 mm, a length of 0.5 mm, and a thicknessof 22.5 μm (copper: 12.5 μm, plated copper: 10 μm, the same as those ofthe wirings). The notched parts were made to have dimensions of a widthof 0.5 mm and a length of 0.5 mm.

Example 2

As Example 2, a printed wiring board was experimentally manufactured asin Example 1 except that the reinforcement layers were provided at theupper surface side (the side formed with the pads) of the base film asshown in FIG. 16. In more detail, the printed wiring board of Example 2was manufactured such that the reinforcement layers at the upper surfaceside were constituted of extended parts extending frontward from theouter side parts of the upper surface side coverlay in the widthdirection.

Comparative Example 1

As Comparative Example 1, a printed wiring board having the samestructure as that of Example 1 was experimentally manufactured exceptthat, as shown in FIG. 25, no reinforcement layers at the lower surfaceside of the base film and no reinforcement layers at the upper surfaceside of the base film were provided.

(Test of Disconnection Resistance)

The test of disconnection resistance was performed through: connectingeach of the flexible printed wiring boards of Examples 1 and 2 andComparative Example 1 with a connector having the structure shown inFIG. 19 (but no contacts were provided); obtaining a state in which theprinted wiring board was simply fitted with and held by the tab-likelock members; pulling the flexible printed wiring board from theconnector in the direction of disconnection (opposite direction to thedirection of connection) using a tensile tester; and measuring a loadapplied to the tensile tester when the printed wiring board wasdisconnected from the connector.

(Test Results)

Results of the test were as follows. Given that the load when theflexible printed wiring board of Comparative Example 1 was disconnectedfrom the connector was represented by 100%, the load when the flexibleprinted wiring board was disconnected from the connector was 146% inExample 1, and 168% in Example 2. It has thus been confirmed that thedisconnection resistance of the flexible printed wiring board isimproved by applying the present invention.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, it is possibleto provide a printed wiring board that exhibits excellent disconnectionresistance.

DESCRIPTION OF REFERENCE NUMERALS

-   1 . . . Flexible printed wiring board-   3 . . . Base film-   4 . . . Adhesive layer-   5 . . . Upper surface side coverlay-   5 a, 5 b . . . Insulating layer (extended part)-   6 . . . Adhesive layer-   7 . . . Lower surface side coverlay-   9, 11 . . . Wiring-   13 . . . Connection end portion-   15 a . . . Pads of front array-   17 a . . . Pads of rear array-   18, 19 . . . Plated layer-   21 . . . Adhesive layer-   23 . . . Reinforcement film-   24, 25 . . . Via-   28, 29 . . . Engageable part-   31, 32 . . . Reinforcement layer (first reinforcement layer)-   34, 35, 34′, 35′, 5 a′, 5 b′ . . . Reinforcement layer (second    reinforcement layer)-   36, 37 . . . Copper foil-   39 . . . Double-sided copper clad laminate-   40, 40′ . . . Electromagnetic wave shield layer-   41, 42 . . . Blind via hole-   50 . . . Connector-   52 . . . Housing-   54 . . . Contact-   56 . . . Rotative member (operative member)-   58 . . . Lock member (engagement part)-   65 . . . Cam-   70 . . . Connector-   72 . . . Housing-   74 . . . Contact-   76 . . . Slider

1-8. (canceled)
 9. A printed wiring board comprising: a base substrate;a plurality of pads for electrical connection that are disposed at onesurface side of the base substrate and at a connection end portion to beconnected with a connector, the plurality of pads forming front and reartwo arrays when viewed in a direction of connection with the connector;first wirings that are provided at the other surface side of the basesubstrate and connected with pads of the front array of the plurality ofpads via vias penetrating the base substrate; and second wirings thatare provided at the one surface side of the base substrate and connectedwith pads of the rear array of the plurality of pads, wherein the firstwirings are provided so as to pass through respective positions at theother surface side of the base substrate corresponding to the pads ofthe front array and the pads of the rear array, the first wirings havefirst expanded-width parts provided at positions on the other surfaceside of the base substrate corresponding to the pads of the front arrayand second expanded-width parts provided at positions on the othersurface side of the base substrate corresponding to the pads of the reararray, the first expanded-width parts have shapes corresponding toshapes of the pads of the front array, and the second expanded-widthparts have shapes corresponding to shapes of the pads of the rear array.10. The printed wiring board according to claim 9, comprising: anengageable part that is formed at a side edge part of the connection endportion and is to be engaged with the connector in a direction ofdisconnection; and a first reinforcement layer that is provided at theother surface side of the base substrate and at a frontward side withrespect to the engageable part when viewed in a direction of connectionwith the connector.
 11. The printed wiring board according to claim 10,wherein the first reinforcement layer is formed integrally with any ofthe first wirings.
 12. The printed wiring board according to claim 10,wherein the first reinforcement layer is formed separately from thefirst wirings.
 13. The printed wiring board according to claim 9,comprising: an engageable part that is formed at a side edge part of theconnection end portion and is to be engaged with the connector in adirection of disconnection; and a second reinforcement layer that isprovided at the one surface side of the base substrate and at afrontward side with respect to the engageable part when viewed in adirection of connection with the connector, wherein the secondreinforcement layer is provided integrally with at least any one of thepads and the second wirings.
 14. A connecter connecting the printedwiring board according to claim 9 with another wiring board, theconnector comprising: a housing that has an insertion opening into whichthe connection end portion of the printed wiring board is inserted; anda plurality of contacts that are provided to correspond to the pluralityof pads of the printed wiring board inserted in the housing.